Intermittent power problems

[Deleted member 74601]

Hey guys,

I have a problem on my Leon which I need some help diagnosing.

Every now and then, the car will all of a sudden feel down on power, and suffer quite a big reduction in mpg (10-15%). My car is 105bhp, and feels more like an 80bhp car when this happens. If I put my foot down, it feels as though it is barely pulling at all, kind of like you can't feel the turbo kicking in.

The other thing I noticed is that the car appears to be slowing down quicker, and that I can't coast as far as usual (in gear or in neutral, but it's much more noticeable in gear). It kind of feels like that when the car is driving, it's trying to engine brake all the time, and when you take your foot off the accelerator, the engine braking is harder than usual.

The problem appears to be quite random. For instance, it happened on the tank of fuel before last for a couple of days and then cured itself. It didn't happen at all on the last tank, but has been happening for the last 2 days (around 350 miles worth of driving). When it goes away, it does so without me changing anything.

I have checked tyre pressures, and they are normal. I have also checked that the brakes are not sticking, but after coming off the motorway yesterday when I was experiencing the problem, the brakes were stone cold.

I can only think it might be the following:

MAF Sensor - I have Vag com, is there anyway I could check this?

Cold weather - I did notice that one the previous tank where I had no issues, the weather was a fair bit warmer than the current tank. (around 12-16c, as opposed to around 3-8c). I had a problem when I first bought the car that when it was started cold it never really reached full fuel efficiency, and felt slightly down on power, however if you stopped the engine for a short period and restarted it, it was fine. This went away over the summer, and I was thinking the cold weather could possibly be bringing this problem back?

Turbo problem - I have had a whistling noise on the car at speeds above 40mph (mainly around 40 and 50mph), however it doesn't sound like the 'siren' noise you hear of, more like a constant whistle. It doesn't change pitch when accelerating.

Can anyone advise me on what they think could be causing the problem, and maybe how I could check the MAF?

Thanks guys.

P.S Vag Com shows no fault codes

 

[m0rk]

Is it not doing its dpf regen?

 

[Deleted member 74601]

Is it not doing its dpf regen?

Well, it's felt like that for the last 2 days at the moment, in which I've done about 350-400 miles of driving. When the problem occurred previously, the lack of power and mpg problems were noticeable it lasted around 300-400 miles.

It usually lasts a couple of days and then goes away, but obviously, I don't know if it's related to temperature or anything.

 

[Deleted member 74601]

Anyone else?

It's starting to piss me off now

 

[EndlessNameless]

If it's engine related, I can't see how it could affect your coasting in neutral.

I'd check all the bearings and so on between the gearbox and the wheels, or maybe it's somewhere inside the gearbox. No idea how you'd check that though.

 

[Deleted member 74601]

Yeah.

It's maybe not affecting the coasting in neutral really, it's been harder to tell as I've driven it more whilst it's behaving like this. Definitely slowing quicker when in gear though, mpg down, and power certainly down. I've been putting my foot down in 3rd at about 1500/1600RPM and it's as though the car has no turbo, until about 2 seconds late it realises it does have one and starts to use it.

I've picked up some tips on how to run some test on the MAF and Turbo using VAG COM from another forum. So I'll give those again and see if I can spot anything.

Otherwise it might be a trip to the dealers if no one else can suggest anything